The dental and medical clinicians of the Clinical/Laboratory Core will see all patients referred by the epidemiology cohorts and validate diagnoses. From these referrals and other sources of patient referrals, they will continue to build clinical cohorts of patients with specific oral lesions in order to analyze their relationship to the development of AIDS and to other markers/predictors. They will obtain samples and biopsies for the studies in Projects 4 and 5 from well-characterized patients with the oral lesions being studied. The core staff will be responsible for clinical research patient charts and records, for appointments, for follow-up calls concerning outcome, for specimen handling and storage and for getting specimens to Project 4 and 5 investigators. They will stain smears and sections, handle samples and biopsy tissue, maintain pathology and other clinical laboratory data, perform in situ hybridization for Epstein-Barr virus to confirm the diagnosis of hairy leukoplakia and provide electronmicroscopy services. The Clinical/Laboratory Core investigators will continue to study the clinical and pathological features of the oral manifestations of HIV infection and, in conjunction with Project 1, 4 and 5 investigators, will continue to report new features and to explore their etiology, pathogenesis and response to therapy. Part of the responsibilities of the investigators in the Cores and Projects will be to continue to document and publish such new findings and to conceive and test new hypotheses concerning this fascinating and challenging group of diseases.